/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_sparse_q15.c
*
* Description:	Q15 sparse FIR filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* ------------------------------------------------------------------- */
#include "arm_math.h"

/**
 * @addtogroup FIR_Sparse
 * @{
 */

/**
 * @brief Processing function for the Q15 sparse FIR filter.
 * @param[in]  *S           points to an instance of the Q15 sparse FIR structure.
 * @param[in]  *pSrc        points to the block of input data.
 * @param[out] *pDst        points to the block of output data
 * @param[in]  *pScratchIn  points to a temporary buffer of size blockSize.
 * @param[in]  *pScratchOut points to a temporary buffer of size blockSize.
 * @param[in]  blockSize    number of input samples to process per call.
 * @return none.
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using an internal 32-bit accumulator.
 * The 1.15 x 1.15 multiplications yield a 2.30 result and these are added to a 2.30 accumulator.
 * Thus the full precision of the multiplications is maintained but there is only a single guard bit in the accumulator.
 * If the accumulator result overflows it will wrap around rather than saturate.
 * After all multiply-accumulates are performed, the 2.30 accumulator is truncated to 2.15 format and then saturated to 1.15 format.
 * In order to avoid overflows the input signal or coefficients must be scaled down by log2(numTaps) bits.
 */


void arm_fir_sparse_q15(
    arm_fir_sparse_instance_q15* S,
    q15_t* pSrc,
    q15_t* pDst,
    q15_t* pScratchIn,
    q31_t* pScratchOut,
    uint32_t blockSize)
{

	q15_t* pState = S->pState;                     /* State pointer */
	q15_t* pIn = pSrc;                             /* Working pointer for input */
	q15_t* pOut = pDst;                            /* Working pointer for output */
	q15_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
	q15_t* px;                                     /* Temporary pointers for scratch buffer */
	q15_t* pb = pScratchIn;                        /* Temporary pointers for scratch buffer */
	q15_t* py = pState;                            /* Temporary pointers for state buffer */
	int32_t* pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
	uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
	uint16_t numTaps = S->numTaps;                 /* Filter order */
	int32_t readIndex;                             /* Read index of the state buffer */
	uint32_t tapCnt, blkCnt;                       /* loop counters */
	q15_t coeff = *pCoeffs++;                      /* Read the first coefficient value */
	q31_t* pScr2 = pScratchOut;                    /* Working pointer for pScratchOut */


#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	q31_t in1, in2;                                /* Temporary variables */


	/* BlockSize of Input samples are copied into the state buffer */
	/* StateIndex points to the starting position to write in the state buffer */
	arm_circularWrite_q15(py, delaySize, &S->stateIndex, 1, pIn, 1, blockSize);

	/* Loop over the number of taps. */
	tapCnt = numTaps;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = (S->stateIndex - blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Working pointer for state buffer is updated */
	py = pState;

	/* blockSize samples are read from the state buffer */
	arm_circularRead_q15(py, delaySize, &readIndex, 1,
	                     pb, pb, blockSize, 1, blockSize);

	/* Working pointer for the scratch buffer of state values */
	px = pb;

	/* Working pointer for scratch buffer of output values */
	pScratchOut = pScr2;

	/* Loop over the blockSize. Unroll by a factor of 4.
	 * Compute 4 multiplications at a time. */
	blkCnt = blockSize >> 2;

	while(blkCnt > 0u) {
		/* Perform multiplication and store in the scratch buffer */
		*pScratchOut++ = ((q31_t) * px++ * coeff);
		*pScratchOut++ = ((q31_t) * px++ * coeff);
		*pScratchOut++ = ((q31_t) * px++ * coeff);
		*pScratchOut++ = ((q31_t) * px++ * coeff);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4,
	 * compute the remaining samples */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		/* Perform multiplication and store in the scratch buffer */
		*pScratchOut++ = ((q31_t) * px++ * coeff);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Load the coefficient value and
	 * increment the coefficient buffer for the next set of state values */
	coeff = *pCoeffs++;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = (S->stateIndex - blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Loop over the number of taps. */
	tapCnt = (uint32_t) numTaps - 1u;

	while(tapCnt > 0u) {
		/* Working pointer for state buffer is updated */
		py = pState;

		/* blockSize samples are read from the state buffer */
		arm_circularRead_q15(py, delaySize, &readIndex, 1,
		                     pb, pb, blockSize, 1, blockSize);

		/* Working pointer for the scratch buffer of state values */
		px = pb;

		/* Working pointer for scratch buffer of output values */
		pScratchOut = pScr2;

		/* Loop over the blockSize. Unroll by a factor of 4.
		 * Compute 4 MACS at a time. */
		blkCnt = blockSize >> 2;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			*pScratchOut++ += (q31_t) * px++ * coeff;
			*pScratchOut++ += (q31_t) * px++ * coeff;
			*pScratchOut++ += (q31_t) * px++ * coeff;
			*pScratchOut++ += (q31_t) * px++ * coeff;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* If the blockSize is not a multiple of 4,
		 * compute the remaining samples */
		blkCnt = blockSize % 0x4u;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			*pScratchOut++ += (q31_t) * px++ * coeff;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* Load the coefficient value and
		 * increment the coefficient buffer for the next set of state values */
		coeff = *pCoeffs++;

		/* Read Index, from where the state buffer should be read, is calculated. */
		readIndex = (S->stateIndex - blockSize) - *pTapDelay++;

		/* Wraparound of readIndex */
		if(readIndex < 0) {
			readIndex += (int32_t) delaySize;
		}

		/* Decrement the tap loop counter */
		tapCnt--;
	}

	/* All the output values are in pScratchOut buffer.
	   Convert them into 1.15 format, saturate and store in the destination buffer. */
	/* Loop over the blockSize. */
	blkCnt = blockSize >> 2;

	while(blkCnt > 0u) {
		in1 = *pScr2++;
		in2 = *pScr2++;

#ifndef  ARM_MATH_BIG_ENDIAN

		*__SIMD32(pOut)++ =
		    __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
		            16);

#else
		*__SIMD32(pOut)++ =
		    __PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16),
		            16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

		in1 = *pScr2++;

		in2 = *pScr2++;

#ifndef  ARM_MATH_BIG_ENDIAN

		*__SIMD32(pOut)++ =
		    __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
		            16);

#else

		*__SIMD32(pOut)++ =
		    __PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16),
		            16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */


		blkCnt--;

	}

	/* If the blockSize is not a multiple of 4,
	   remaining samples are processed in the below loop */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		*pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
		blkCnt--;
	}

#else

	/* Run the below code for Cortex-M0 */

	/* BlockSize of Input samples are copied into the state buffer */
	/* StateIndex points to the starting position to write in the state buffer */
	arm_circularWrite_q15(py, delaySize, &S->stateIndex, 1, pIn, 1, blockSize);

	/* Loop over the number of taps. */
	tapCnt = numTaps;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = (S->stateIndex - blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Working pointer for state buffer is updated */
	py = pState;

	/* blockSize samples are read from the state buffer */
	arm_circularRead_q15(py, delaySize, &readIndex, 1,
	                     pb, pb, blockSize, 1, blockSize);

	/* Working pointer for the scratch buffer of state values */
	px = pb;

	/* Working pointer for scratch buffer of output values */
	pScratchOut = pScr2;

	blkCnt = blockSize;

	while(blkCnt > 0u) {
		/* Perform multiplication and store in the scratch buffer */
		*pScratchOut++ = ((q31_t) * px++ * coeff);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Load the coefficient value and
	 * increment the coefficient buffer for the next set of state values */
	coeff = *pCoeffs++;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = (S->stateIndex - blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Loop over the number of taps. */
	tapCnt = (uint32_t) numTaps - 1u;

	while(tapCnt > 0u) {
		/* Working pointer for state buffer is updated */
		py = pState;

		/* blockSize samples are read from the state buffer */
		arm_circularRead_q15(py, delaySize, &readIndex, 1,
		                     pb, pb, blockSize, 1, blockSize);

		/* Working pointer for the scratch buffer of state values */
		px = pb;

		/* Working pointer for scratch buffer of output values */
		pScratchOut = pScr2;

		blkCnt = blockSize;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			*pScratchOut++ += (q31_t) * px++ * coeff;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* Load the coefficient value and
		 * increment the coefficient buffer for the next set of state values */
		coeff = *pCoeffs++;

		/* Read Index, from where the state buffer should be read, is calculated. */
		readIndex = (S->stateIndex - blockSize) - *pTapDelay++;

		/* Wraparound of readIndex */
		if(readIndex < 0) {
			readIndex += (int32_t) delaySize;
		}

		/* Decrement the tap loop counter */
		tapCnt--;
	}

	/* All the output values are in pScratchOut buffer.
	   Convert them into 1.15 format, saturate and store in the destination buffer. */
	/* Loop over the blockSize. */
	blkCnt = blockSize;

	while(blkCnt > 0u) {
		*pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
		blkCnt--;
	}

#endif /*   #ifndef ARM_MATH_CM0 */

}

/**
 * @} end of FIR_Sparse group
 */
